1. Field of the Invention
The present invention relates generally to a method of forming bump electrodes provided on the reverse side of a circuit board or an electronic component, and more particularly, to a method of efficiently forming bump electrodes using simple facilities.
2. Description of the Prior Art
In many cases, bump electrodes have been conventionally formed on the reverse side of a circuit board utilizing ceramics or an electronic component such as a hybrid IC so as to increase integration density. The bump electrode means an electrode formed in a shape swollen out of a surface on which electrodes are to be formed. A conventional method of forming bump electrodes will be described with reference to FIG. 4. In FIG. 4, bump electrodes 2 and 3 are formed on a reverse surface 1a of a circuit board 1 made of ceramics (the circuit board 1, however, is so illustrated that the reverse surface faces up).
The bump electrodes 2 and 3 are formed on the reverse surface 1a of the circuit board 1 by brazing metal balls 4 and 5 using braze metals 6 and 7.
The reason why projected shapes of the bump electrodes 2 and 3 are formed using the metal balls 4 and 5 is that it is easy to make the heights of portions projected from the reverse surface 1a of the circuit board 1 equal to each other.
Since the metal balls 4 and 5 are brazed using the braze metals 6 and 7, however, an apparatus for applying heat to a high temperature is required, resulting in large-scaled facilities. Furthermore, the production processes are complicated.